A conventional manual wheelchair is illustrated in FIGS. 1 and 2. Conventional manual wheelchairs 50 typically comprise a foldable frame 52, a seat 54 and a backrest 56, and a pair of manual brake mechanisms 58a and 58b. Two large drive wheels 60a and 60b are typically rotatably mounted to the foldable frame 52 to permit a user to operate and move the wheelchair. The manually operated hand brakes 58a and 58b are coupled to the wheelchair to engage and prevent rotational movement of the drive wheels. Conventional wheelchairs 50 also typically include leg rests 62 and armrests 64 for the comfort of the user.
The manual brake mechanisms 58a and 58b allow either a user or an attendant to lock the wheels of the wheelchair when exiting, for example, so that the chair does not move away when a patient attempts to enter or exit. Although the conventional manual brake mechanisms are sufficient for their intended purpose once engaged, the requirement that the user must remember to actuate the brakes leaves these devices susceptible to user error. For example, a conventional wheelchair will remain freely moveable if a user or attendant forgets to manually pivot the braking device and lock the wheels. The wheelchair may also remain freely moveable if a user or attendant does not fully apply the manual braking device to the wheels. As a result, a user attempting to stabilize themselves while entering or leaving the wheelchair, is at an increased risk of falling and injury due to the freely moveable wheelchair moving out from beneath them.
Attempts have been made to devise wheelchair-braking devices that automatically engage a wheel of a wheelchair when a user attempts to enter or leave the seat. For example, U.S. Pat. No. 5,894,912 to Dobben includes a sensing lever that senses when a user is entering or leaving the seat of a wheelchair. When the sensing lever senses a user exiting the seat it causes a braking lever to engage the wheels, thereby preventing free movement of the wheelchair. While the design of the wheelchair-braking device in Dobben fulfills its intended purpose, it has at least one significant shortcoming. In particular, the sensing lever, disposed beneath the seat, is continuously biased against a seated user. The continuously biased state of the sensing lever creates uncomfortable pressure points that are continuously felt by the seated user. These pressure points may additionally promote development of sores by the patient.
Another attempt at devising an automatic braking-device for a wheelchair is illustrated in U.S. Pat. No. 6,371,503 to Ritchie, et al. Ritchie discloses an L-shaped actuator that confronts a rear portion of the seat of a wheelchair. When a user sits in the wheelchair the seat engages the L-shaped actuator, which releases the braking-device. The actuator continues to press against the seated user until they exit the wheelchair. The automatic braking-device of Ritchie is susceptible to the same shortcomings as Dobben discussed above. In particular, the constant pressure by the actuator on the seated user creates a pressure point.
Other attempts to invent automatic braking-devices for wheelchairs have resulted in undesirably complicated braking assemblies. For example, U.S. Pat. No. 4,620,818 to Knoche, discloses a wheelchair having a sliding side frame that engages a pair of brake arms pivotally coupled to the wheelchair. The brake arms engage the wheels of the wheelchair as a user sits in the seat. Not only is the automatic braking assembly disclosed in Knoche overly-complicated, it also requires a user to modify the wheelchair's existing brake system. In particular, each of the brake arms includes a transverse portion that replaces the conventional manual wheelchair device. As a result, the modified wheelchair has only one braking device. Additionally, modifying the wheelchair in order to attach the transverse portion of the braking assembly may result in voiding the warranty of the wheelchair.
Still other attempts to resolve the problem associated with conventional wheelchair braking systems have resulted in modified wheelchair frames. For example, U.S. Pat. No. 5,984,334 to Dugas discloses a wheelchair with a moveable seat operationally coupled to a braking mechanism that locks one or more wheels when a user attempts to exit the seat. Another example of a modified device is U.S. Pat. No. 5,451,193 to Pickard. Pickard discloses a new wheelchair having four wheels of the same size. Additionally, the Pickard wheelchair is convertible to a walker. The custom nature of the Dugas and Pickard wheelchairs results in higher manufacturing costs, which are typically passed on to the consumer resulting in a more expensive wheelchair.
Another disadvantage with the previous attempts to provide automatic brake devices to a wheelchair is that the brake devices disable the manual wheelchair's ability to fold for storage or transport.
There remains a need in the wheelchair industry to provide an automatic braking mechanism that intervenes and prevents injuries caused by a freely movable wheelchair rolling out beneath a user as they attempt to enter or leave the seat portion, while addressing manufacturing, operability, cost and functional design issues.